There is a critical unmet need in the field of medicine for non-invasive measurement of respiratory parameters in spontaneously breathing patients. Presently, most respiratory monitoring equipment is used for patients receiving mechanical ventilation. Because most mechanically ventilated patients are intubated, many respiratory parameters can be precisely measured in a way not possible with non-intubated patients. Such parameters include those obtained from capnometry, (end tidal CO2 [EtCO2], respiratory rate and CO2 waveform measurements) and those obtained from respiratory monitors such as differential pressure transducers, absolute pressure transducers and flow transducers (tidal volume [VT], airway pressure [Paw], minute ventilation [VE], respiratory rate [RR], respiratory effort/work of breathing [RE/WOB], inspiratory:expiratory ratio [I:E] and deadspace measurements).
Thus, while patients in the OR and ICU may receive intensive respiratory monitoring, similarly reliable monitoring is not presently available for non-intubated patients who are often ambulatory, such as those on general care floors and other areas of the hospital. Numerous organizations, including the U.S. Food and Drug Administration, the American Society of Anesthesiologists, and the Anesthesia Patient Safety Foundation, have noted this lack of monitoring to be problematic and are calling for new technological advances to migrate intensive respiratory monitoring to non-intubated patients. There is also a critical need for improved monitoring of patients receiving patient controlled anesthesia (PCA) since some central nervous system depressants such as opioids may lead to respiratory depression and subsequent morbidity or mortality. Efforts to preemptively identify patients likely to suffer respiratory depression or respiratory arrest have been only partially successful and adequate monitoring solutions are still lacking even if such patients are identified.